Traumatic Subcutaneous Emphysema

This Patient Is Like a Balloon, What Should I Do?

“I wondered what you would do if you have a severe trauma case (such as with massive pneumothorax) and you discover that there is massive subcutaneous emphysema reaching from the thorax site all the way up to the head. Do you do anything about the emphysema?” (Sandy Karl)

I received this question from a Veterinary ECC Small Talker – thanks Sandy! – and thought I would share some thoughts. I am not going to reference any literature here, to be fair I don’t know if there are any clinical papers looking at this patient population. 

What I would say is that you need to make the decision with respect to surgical versus conservative management on an individual case basis based on factors such as:

  • The suspected source of air and severity of injury
  • The mechanism of trauma e.g. blunt trauma versus bite wounds
  • Other concurrent injuries that may be present
  • The patient's clinical status and stability for anaesthesia/surgery

And clearly some 'wait and see' cases may end up having surgery.

 
(Picture: Liron Hirsch)

(Picture: Liron Hirsch)

The underlying aetiology of the subcutaneous emphysema is important - if known. In her message Sandy mentions a patient with a pneumothorax. It is said that one of the most common causes of subcutaneous emphysema is rupture of the marginal alveoli, what some people refer to as the Macklin effect, secondary to blunt trauma. The air tracks up through the cervical tissue planes and you get subcutaneous emphysema. The majority of these blunt trauma cases resolve without any specific intervention.

If during this ‘wait and see’ period you feel that the subcutaneous emphysema is so severe as to be causing the patient significant morbidity or discomfort then you could drain some of it via needle aspiration/puncture, potentially at multiple sites. I would say however that if you find yourself wanting to do this more than once or maybe twice, it would probably be worth rethinking your approach to the case, reconsidering the source of the air leakage and whether a more definitive approach is needed. And certainly if you feel that the subcutaneous emphysema is sufficiently bad that you are thinking of placing a subcutaneous drain then I would definitely encourage you to reassess your overall management plan again first.

With respect to the underlying aetiology for subcutaneous emphysema then I think most people probably agree that bite wounds (‘tip of the iceberg’) or penetrating injuries should be surgically explored.

Diagnostic imaging is useful in trying to understand the extent and possible underlying cause of subcutaneous emphysema as well as concurrent injuries. For example rupture of the trachea may be apparent by an increase in distance between the individual tracheal rings, but it is also important to realise that even if there is a rupture there may be a pseudomembrane covering the rupture site. As a result you must be careful when anaesthetising these patients, have an appropriate length endotracheal tube and avoid IPPV.

Understanding the anatomy is important. Where has the subcutaneous emphysema come from? Directly from the pleural cavity? From the mediastinal structures? Also remember that the mediastinum is continuous with the retroperitoneum via the aortic hiatus, so you could get a patient with subcutaneous emphysema, pneumomediastinum and pneumoretroperitoneum. If this occurs the clinician should be thinking of causes of pneumomediastinum and ruling them out by appropriate tests e.g. endoscopy of the oesophagus etc. – and not exploring the abdomen!

The other thing to keep in mind is that you could have a patient with subcutaneous emphysema that then gives rise to pneumomediastinum due to tracking of air along the fascial planes, and potentially they could even get some degree of pneumothorax. Reminding yourself about the anatomy and the potential sources and routes of air is important in these cases especially as we don’t see these cases all that often.

All of that said my personal experience is that the patients – often cats – that have subcutaneous emphysema from blunt trauma typically just need conservative management, gentle handling and a tincture of time as far as the emphysema is concerned…but obviously each case has to be approached individually. Furthermore we do not necessarily always identify a specific cause for the emphysema, a specific source of air. Sometimes it is not felt in the patient's best interest to pursue the necessary investigations and he/she recovers without a definitive source being identified.

As always, I would really love to hear your thoughts and experiences here.

Have you seen many of these cases?
How often have you drained subcutaneous emphysema or seen others drain it
?
Any important points I have failed to mention?